Ever stricter legal regulations regarding the permissible pollutant emissions from vehicles equipped with internal combustion engines make it necessary to minimize the pollutant emissions, at least within specified operating ranges of the internal combustion engine. One way of achieving this is to reduce the pollutant emissions which are generated during the combustion of the air/fuel mixture in the particular cylinder of the internal combustion engine. Another method is the use of emission control systems in internal combustion engines which convert the pollutant emissions produced during the combustion process of the air/fuel mixture in the particular cylinders into harmless substances. Catalytic converters which can convert the carbon monoxide, hydrocarbons and nitrogen oxides into harmless substances are used for this purpose.
A precondition for a long-term good conversion capability of catalytic converters is that no overheating of the catalytic converters takes place. For this reason, it is necessary, particularly in operating areas of the internal combustion engine in which very high performance is to be provided by the internal combustion engine, to take measures as appropriate to protect against overheating of the catalytic converter. For this purpose, a determination of the exhaust gas temperature and/or the component temperature of the catalytic converter which is as accurate as possible is desirable.
From DE 10 2004 033 394 B3, an engine control unit is known which sets an exhaust gas temperature by means of the air/fuel mixture and which includes a temperature model that calculates the temperature for a component to be protected in the exhaust gas tract. By means of the temperature model, a set temperature, which is maintained for a long period provided the current operating and driving conditions are maintained, is determined for the component arranged in the exhaust gas tract. The set temperature is the component temperature, which is established during continuous operation of the component to be protected. To protect the component, the engine control unit controls the exhaust gas temperature as a function of the set temperature.